<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Vue 测试实例 - 菜鸟教程(runoob.com)</title>
    <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
</head>
<body>
<div id = "app">
    <p style = "font-size:25px;">计数器: {{ counter }}</p>
    <button @click = "counter++" style = "font-size:25px;">点我</button>
</div>
<script type = "text/javascript">
    var vm = new Vue({
        el: '#app',
        data: {
            counter: 1
        }
    });
    vm.$watch('counter', function(nval, oval) {
        alert('计数器值的变化 :' + oval + ' 变为 ' + nval + '!');
    });
    setTimeout(
        function(){
            vm.counter += 20;
        },10000
    );
</script>
</body>
</html>